The present invention relates to the use of EP4-receptor agonists and partial agonists to stimulate mucin secretion to treat dry eye, keratoconjunctivitis, Sjogren""s syndrome and related ocular surface diseases.
Dry eye is a common ocular surface disease afflicting millions of people in the U.S. each year, especially the elderly (Schein et al., Prevalence of dry eye among the elderly. American J. Ophthalmology, 124:723-738, (1997)). Dry eye may afflict an individual with varying severity. In mild cases, a patient may experience burning, a feeling of dryness, and persistent irritation such as is often caused by small bodies lodging between the eye lid and the eye surface. In severe cases, vision may be substantially impaired. Other diseases, such as Sjogren""s disease and cicatricialpemphigoid manifest dry eye complications.
Although it appears that dry eye may result from a number of unrelated pathogenic causes, the common end result is the breakdown of the tear film, which results in dehydration of the exposed outer surface of the eye. (Lemp, Report of the Nation Eye Institute/Industry Workshop on Clinical Trials in Dry Eyes, The CLAO Journal, 21(4):221-231 (1995)). Four events have been identified which singly or in combination are believed to result in the dry eye condition: a) decreased tear production or increased tear evaporation; b) decreased conjunctival goblet-cell density; c) increased corneal desquamation; and d) destabilization of the cornea-tear interface (Gilbard, Dry eye: pharmacological approaches, effects, and progress. The CLAO Journal, 22:141-145 (1996)). Another major problem is the decreased mucin production by the conjunctival cells and/or corneal epithelial cells of mucin, which protects and lubricates the ocular surface (Gipson and Inatomi, Mucin genes expressed by ocular surface epithelium. Progress in Retinal and Eye Research, 16:81-98 (1997)).
Practitioners have taken several approaches to the treatment of dry eye. One common approach has been to supplement and stabilize the ocular tear film using so-called artificial tears instilled throughout the day. Another approach has been the use of ocular inserts that provide a tear substitute or to stimulate endogenous tear production.
Examples of the tear substitution approach include the use of buffered, isotonic saline solutions, aqueous solutions containing water soluble polymers that render the solutions more viscous and thus less easily shed by the eye. Tear reconstitution is also attempted by providing one or more components of the tear film such as phospholipids and oils. Examples of these treatment approaches are disclosed in U.S. Pat. No. 4,131,651 (Shah et al.), U.S. Pat. No. 4,370,325 (Packman), U.S. Pat. No. 4,409,205 (Shively), U.S. Pat. Nos. 4,744,980 and 4,883,658 (Holly), U.S. Pat. No. 4,914,088 (Glonek), U.S. Pat. No. 5,075,104 (Gressel et al.) and U.S. Pat. No. 5,294,607 (Glonek et al.).
United States Patents directed to the use of ocular inserts in the treatment of dry eye include U.S. Pat. No. 3,991,759 (Urquhart). Other semi-solid therapy has included the administration of carrageenans (U.S. Pat. No. 5,403,841, Lang) which gel upon contact with naturally occurring tear film.
Another recent approach involves the provision of lubricating substances in lieu of artificial tears. U.S. Pat. No. 4,818,537 (Guo) discloses the use of a lubricating, liposome-based composition.
Aside from the above efforts, which are directed primarily to the alleviation of symptoms associated with dry eye, methods and compositions directed to treatment of the dry eye condition have also been pursued. For example, U.S. Pat. No. 5,041,434 (Lubkin) discloses the use of sex steroids, such as conjugated estrogens, to treat dry eye condition in post-menopausal women; U.S. Pat. No. 5,290,572 (MacKeen) discloses the use of finely divided calcium ion compositions to stimulate tear film; and U.S. Pat. No. 4,966,773 (Gressel et al.) discloses the use of microfine particles of one or more retinoids for ocular tissue normalization.
Although these approaches have met with some success, problems in the treatment of dry eye nevertheless remain. The use of tear substitutes, while temporarily effective, generally requires repeated application over the course of a patient""s waking hours. It is not uncommon for a patient to have to apply artificial tear solution ten to twenty times over the course of the day. Such an undertaking is not only cumbersome and time consuming, but is also potentially very expensive.
The use of ocular inserts is also problematic. Aside from cost, they are often unwieldy and uncomfortable. Further, as foreign bodies introduced in the eye, they can be a source of contamination leading to infections. In situations where the insert does not itself produce and deliver a tear film, artificial tears must still be delivered on a regular and frequent basis.
In view of the foregoing, there is a clear need for an effective treatment for dry eye that is capable of alleviating symptoms, as well as treating the underlying physical and physiological deficiencies of dry eye, and that is both convenient and inexpensive to administer.
Mucins are proteins which are heavily glycosylated with glucosamine-based moieties. Mucins provide protective and lubricating effects to epithelial cells, especially those of mucosal membranes. Mucins have been shown to be secreted by vesicles and discharged on the surface of the conjuctival epithelium of human eyes (Greiner et al., Mucus Secretory Vesicles in Conjunctival Epithelial Cells of Wearers of Contact Lenses, Archives of Ophthalmology, 98:1843-1846 (1980); and Dilly et al., Surface Changes in the Anaesthetic Conjunctiva in Man, with Special Reference to the Production of Mucus from a Non-Goblet-Cell Source, British Journal of Ophthalmology, 65:833-842 (1981)). A number of human-derived mucins which reside in the apical and subapical corneal epithelium have been discovered and cloned (Watanabe et al., Human Corneal and Conjuctival Epithelia Produce a Mucin-Like Glycoprotein for the Apical Surface, Investigative Ophthalmology and Visual Science (IOVS), 36(2):337-344 (1995)). Recently, a new mucin was reported to be secreted via the cornea apical and subapical cells as well as the conjunctival epithelium of the human eye (Watanabe et al., IOVS, 36(2):337-344 (1995)). These mucins provide lubrication, and additionally attract and hold moisture and sebacious material for lubrication and the corneal refraction of light.
Mucins are also produced and secreted in other parts of the body including lung airway passages, and more specifically from goblet cells interspersed among tracheal/bronchial epithelial cells. Certain arachidonic acid metabolites have been shown to stimulate mucin production in these cells. Yanni reported the increased secretion of mucosal glycoproteins in rat lung by hydroxyeicosatetraenoic acid (xe2x80x9cHETExe2x80x9d) derivatives (Yanni et al, Effect of intravenously Administered Lipoxygenase Metabolites on Rat Tracheal Mucous Gel Layer Thickness, International Archives of Allergy And Applied Immunology, 90:307-309 (1989)).
The conventional treatment for dry eye, as discussed above, includes administration of artificial tears to the eye several times a day. Other agents claimed for increasing ocular mucin and/or tear production include vasoactive intestinal polypeptide (Dartt et al. Vasoactive intestinal peptide-stimulated glycocongiugate secretion from conjunctival goblet cells. Experimental Eye Research, 63:27-34, (1996)), gefarnate (Nakmura et al. Gefarnate stimulates secretion of mucin-like glycoproteins by corneal epithelium in vitro and protects corneal epithelium from dessication in vivo, Experimental Eye Research, 65:569-574 (1997)), and the use of liposomes (U.S. Pat. No. 4,818,537), androgens (U.S. Pat. No. 5,620,921), melanocycte stimulating hormones (U.S. Pat. No. 4,868,154), phosphodiesterase inhibitors (U.S. Pat. No. 4,753,945), retinoids (U.S. Pat. No. 5,455,265) and hydroxyeicosatetraenoic acid derivatives (U.S. Pat. No. 5,696,166). However, many of these compounds or treatments suffer from a lack of specificity, efficacy and potency and none of these agents have been marketed so far as therapeutically useful products to treat dry eye and related ocular surface diseases. Thus, there remains a need for an efficacious therapy for the treatment of dry eye and related diseases.
Additionally, in the gastric mucosal cell-type, prostaglandin E2 (PGE2) has been shown to stimulate mucin secretion via the EP4 receptor-subtype and the mRNA for this receptor has been demonstrated in the gastric mucosal cells (Hassan et al. Presence of prostaglandin EP4 receptor gene expression in a rat gastric mucosal cell line, Digestion, 57:196-200 (1996)); Adami et al. Pharmacological research on gefarnate, a new synthetic isoprenoid with anti-ulcer action. Archives of International Pharmacodynamics. 147:113-145 (1964)).
Prostaglandins are metabolite derivatives of arachidonic acid. Arachidonic acid in the body is converted to prostaglandin G2, which is subsequently converted to prostaglandin H2. Other naturally occurring prostaglandins are derivatives of prostaglandin H2. A number of different types of prostaglandins are known in the art including A, B, C, D, E, F, G, I and J-Series prostaglandins (U.S. Pat. No. 5,151,444; EP 0 561 073 A1; Coleman et al., VIII International Union of Pharmacology classification of prostanoid receptors: Properties, distribution, and structure of the receptors and their subtypes, Pharmacological Reviews, 45:205-229 (1994)). Depending on the number of double-bonds in the xcex1-(top chain) and/or the xcfx89-chain (bottom chain), the prostaglandins are further classified with subscripts such as PGD2, PGE1, PGE2, PGF2xcex1, etc. (U.S. Pat. No. 5,151,444; Coleman et al., VIII International Union of Pharmacology classification of prostanoid receptors: Properties, distribution, and structure of the receptors and their subtypes, Pharmacological Reviews, 45:205-229 (1994)). Whilst these classes of prostaglandins interact preferably with the designated major classes of receptors (e.g. DP, EP, FP) and subclasses of receptors (e.g. EP2, EP3, EP4), the subscripts associated with the prostaglandin does not necessarily correspond with the subclass of the receptor(s) with which they interact. Furthermore, it is well known that these endogenous prostaglandins are non-specific in terms of interacting with the various classes of prostaglandin receptors. Thus, PGE2 not only interacts with EP2 receptors, but can also activate EP1, EP2, EP3 and EP4 receptors (Coleman et al., VIII International Union of Pharmacology classification of prostanoid receptors: Properties, distribution, and structure of the receptors and their subtypes, Pharmacological Reviews, 45:205-229 (1994)). Of interest in the present invention are prostaglandins which are believed to exhibit mucin-producing activity and are based on the structure of PGE2 (an E-series prostaglandin): 
The EP4 prostaglandin receptor belongs to a family of prostaglandin receptors, all of which have seven-transmembrane domains and couple to specific G-proteins. When the EP4 receptor on the cell surface is activated by the binding of a specific agonist ligand (a prostaglandin belonging to one of several defined classes of prostaglandins) the conformation of the G-protein is modified to favor the coupling to the enzyme adenylate cyclase (inside the cell). This event then leads to the hydrolysis of ATP to generate the intracellular second messenger cyclic AMP (cAMP) (Coleman et al., VIII International Union of pharmacology classification of prostanoid receptors: Properties, distribution, and structure of the receptors and their subtypes, Pharmacological Reviews, 45:205-229 (1994)). The cAMP produced in this manner then leads to the activation of various cAMP-dependent enzymes which produce various biochemical events leading to the final biological response which may involve tissue contraction, hormone release or fluid and /or electrolyte secretion amongst other responses.
We have now unexpectedly discovered EP4 receptor mRNA in human primary and immortalized corneal epithelial (CEPI) cells. We previously detected functional EP4 receptors in human conjunctival epithelial cells (Sharif et al., Pharmacological analysis of mast cell mediator and neurotransmitter receptors coupled to adenylate cyclase and phospholipase C on immunocytochemically-defined human conjunctival epithelial cells. J. Ocular Pharmacology and Therapeutics, 13, 321-336 (1997)), and appreciate that both human corneal epithelial cells (Gipson and Inatomi, Mucin genes expressed by the ocular surface epithelium. Progress in Retinal and Eye Research, 16:81-98 (1997)) and conjunctival cells (Dartt et al. Localization of nerves adjacent to goblet cells in rat conjunctiva. Current Eye Research, 14:993-1000 (1995)) are capable of secreting mucins. Hence, the discovery of the presence of EP4 receptors in human corneal and conjunctival epithelial cells prompted us to theorize that a selective EP4 agonist might provide a useful therapy for dry eye.
The present invention is directed to compositions and methods for the treatment of dry eye and other disorders requiring the wetting of the eye. More specifically, the present invention discloses compositions containing EP4 receptor agonists and methods for treating dry eye type disorders.
Preferred compositions include an effective amount of an EP4 receptor agonist for the production of mucins in mammals, and especially in humans. The compositions are administered topically to the eye for the treatment of dry eye.
It has now been discovered that certain EP4 receptor agonists stimulate mucin production in human conjuctival epithelium and are therefore believed to be useful in treating dry eye. As used herein, the term xe2x80x9cEP4 receptor agonistsxe2x80x9d refers to any compound which acts as an agonist or partial agonist at the EP4 receptor, thereby stimulating mucin production and/or secretion in the conjunctival epithelium and goblet cells following topical ocular application. Specifically included in such definition are compounds of the following formula I: 
wherein:
R1=CO2R, CONR4R5, or CH2OR6, where:
R=H or pharmaceutically acceptable cationic salt moiety, or CO2R=pharmaceutically acceptable ester moiety;
R4, R5=same or different=H or alkyl; and
R6=H, acyl, or alkyl;
n=0 or 2;
Y=O, S, or CH2;
one of R9a, R9b=H and the other=OR7, where R7=H, alkyl, or acyl; or, R9bR9a taken together=O as a carbonyl;
X=H, Cl, F, or OR8 in either configuration, where R8=H, alkyl, or acyl;
B=O, or H and OR10 in either configuration, where R10=H, alkyl, or acyl;
xe2x80x94xe2x80x94xe2x80x94xe2x80x94=single or double bond;
R2, R3=same or different=H or alkyl, or R2, R3 may be combined to form a C3-C7 cycloalkyl;
A=H, C2-C6 alkyl, C3-C7 cycloalkyl, (CH2)nxe2x80x2D, (CH2)nxe2x80x2OD, where:
nxe2x80x2=1-4; and
D=
xe2x80x83wherein:
nxe2x80x3=0-3;
Z=H, halogen, C1-C4 alkyl, C1-C4 alkoxy, or CF3; and
Yxe2x80x2=CHxe2x95x90CH, O, or S;
with the proviso that when R2-R3 form a cycloalkyl, then A=H;
with the further provisos that (1) when R9aR9b=O as a carbonyl, then X=H or OR8 in either configuration and Axe2x89xa0(CH2)nxe2x80x2D or (CH2)nxe2x80x2OD; and (2) when one of R9a, R9b=H and the other=OR7, then R2=R3=H and A=(CH2)nxe2x80x2D or (CH2)nxe2x80x2OD.
As used herein, the terms xe2x80x9cpharmaceutically acceptable esterxe2x80x9d/xe2x80x9cpharmaceutically acceptable cationic saltxe2x80x9d means any ester/cationic salt that would be suitable for therapeutic administration to a patient by any conventional means without significant deleterious health consequences; and xe2x80x9cophthalmically acceptable esterxe2x80x9d/xe2x80x9cophthalmically acceptable cationic saltxe2x80x9d means any pharmaceutically acceptable ester/cationic salt that would be suitable for ophthalmic application, i.e. non-toxic and non-irritating. Wavy line attachments indicate that the configuration may be either alpha (xcex1) or beta (xcex2). The carbon numbering is as indicated in formula I, even when n=2. Dashed lines on bonds [e.g., between carbons 4 (C-4) and 5 (C-5)] indicate a single or double bond. Two solid lines present specify the configuration of the relevant double bond. Hatched lines indicate the xcex1 configuration. A solid triangular line indicates the xcex2 configuration.
The term xe2x80x9cacylxe2x80x9d represents a group that is linked by a carbon atom that has a double bond to an oxygen atom and single bond to another carbon atom.
The term xe2x80x9cacylaminoxe2x80x9d represents a group that is linked by an amino atom that is connected to a carbon atom has a double bond to an oxygen group and a single bond to a carbon atom or hydrogen atom.
The term xe2x80x9cacyloxyxe2x80x9d represents a group that is linked by an oxygen atom that is connected to a carbon that has a double bond to an oxygen atom and single bond to another carbon atom.
The term xe2x80x9calkenylxe2x80x9d includes straight or branched chain hydrocarbon groups having 1 to 15 carbon atoms with at least one carbon-carbon double bond. The chain hydrogens may be substituted with other groups, such as halogen. Preferred straight or branched alkeny groups include, allyl, 1-butenyl, 1-methyl-2-propenyl and 4-pentenyl.
The term xe2x80x9calkoxyxe2x80x9d represents an alkyl group attached through an oxygen linkage.
The term xe2x80x9calkylxe2x80x9d includes straight or branched chain aliphatic hydrocarbon groups that are saturated and have 1 to 15 carbon atoms. The alkyl groups may be substituted with other groups, such as halogen, hydroxyl or alkoxy. Preferred straight or branched alkyl groups include methyl, ethyl, propyl, isopropyl, butyl and t-butyl.
The term xe2x80x9calkylaminoxe2x80x9d represents an alkyl group attached through a nitrogen linkage.
The term xe2x80x9calkynylxe2x80x9d includes straight or branched chain hydrocarbon groups having 1 to 15 carbon atoms with at least one carbon-carbon triple bond. The chain hydrogens may be substituted with other groups, such as halogen. Preferred straight or branched alkynyl groups include, 2-propynyl, 2-butynyl, 3-butynyl, 1-methyl-2-propynyl and 2-pentynyl.
The term xe2x80x9carylxe2x80x9d refers to carbon-based rings which are aromatic. The rings may be isolated, such as phenyl, or fused, such as naphthyl. The ring hydrogens may be substituted with other groups, such as lower alkyl, or halogen.
The term xe2x80x9ccarbonylxe2x80x9d represents a group that has a carbon atom that has a double bond to an oxygen atom.
The term xe2x80x9ccarbonylalkoxyxe2x80x9d represents a group that is linked by a carbon atom that has a double bond to an oxygen atom and a single bond to an alkoxy group.
The term xe2x80x9ccarbonyloxylxe2x80x9d represents a group that is linked by a carbon atom that has a double bond to an oxygen atom and a single bond to a second oxygen atom.
The term xe2x80x9ccycloalkylxe2x80x9d includes straight or branched chain, saturated or unsaturated aliphatic hydrocarbon groups which connect to form one or more rings, which can be fused or isolated. The rings may be substituted with other groups, such as halogen, hydroxyl or lower alkyl. Preferred cycloalkyl groups include cyclopropyl, cyclobutyl, cylopentyl and cyclohexyl.
The term xe2x80x9cdialkylaminoxe2x80x9d represents two alkyl groups attached through a nitrogen linkage.
The term xe2x80x9chalogenxe2x80x9d and xe2x80x9chaloxe2x80x9d represents fluoro, chloro, bromo, or iodo.
The term xe2x80x9cheteroarylxe2x80x9d refers to aromatic hydrocarbon rings which contain at least one heteroatom such as O, S, or N in the ring. Heteroaryl rings may be isolated, with 5 to 6 ring atoms, or fused, with 8 to 10 atoms. The heteroaryl ring(s) hydrogens or heteroatoms with open valency may be substituted with other groups, such as lower alkyl or halogen. Examples of heteroaryl groups include imidazole, pyridine, indole, quinoline, furan, thiophene, pyrrole, tetrahydroquinoline, dihydrobenzofuran, and dihydrobenzindole.
The term xe2x80x9clower alkylxe2x80x9d represents alkyl groups containing one to six carbons (C1-C6).
Preferred for purposes of the present invention are those compounds of formula I,
wherein:
R1=CO2R, CONR4R5, or CH2OR6, where:
R=H, lower alkyl, or ophthalmically acceptable salt moiety;
R4=R5=H; and
R6=H or lower alkyl;
n=0;
Y=CH2;
R9a=OH, and R9b=H;
X=OH in the xcex1 configuration;
B=H in the xcex2 configuration and OR10 in the xcex1 configuration, where R10=H or CH3;
R2=R3=H;
A=(CH2)nxe2x80x2D or (CH2)nxe2x80x2OD, where:
nxe2x80x2=1-4; and
D=
xe2x80x83wherein:
nxe2x80x3=0-3;
Z=H, Cl, Br, methyl, methoxy, or CF3; and
Yxe2x80x2=CHxe2x95x90CH, O, or S.
Also preferred for purposes of the present invention are those compounds of formula I, wherein:
R1=CO2R, CONR4R5, or CH2OR6, where
R=H, lower alkyl, or ophthalmically acceptable cationic salt moiety;
R4=R5=H; and
R6=H or lower alkyl;
n=0;
Y=CH2;
R9aR9b=O as a carbonyl;
X=H, or OH in the xcex1 configuration;
xe2x80x94xe2x80x94xe2x80x94xe2x80x94= single or double bond;
B=H in the xcex2 configuration and OH in the xcex1 configuration;
R2=R3=H or CH3; and
A=n-butyl.
Examples of most preferred compounds are the following: 11-deoxy-PGE1, 11-deoxy-16,16,-dimethyl-PGE2, 16,16-dimethyl-PGE2 [all of which are commercially available from Cayman Chemical Co (Ann Arbor, Mich.)] as well as the following prostaglandin analogs disclosed in WO 97/31895: 7-[3xcex1,5xcex1-dihydroxy-2-(3xcex1hydroxy-5-(5-(2,3-dibromo)thienyl)-1E-pentenyl)cyclopentyl]-5Z-heptenoic acid; 7-[3xcex1,5xcex1-dihydroxy-2-(3xcex1-hydroxy-5-(2-methyl)furanyl-1E-pentenyl) cyclopentyl]-5Z-heptenoic acid; 7-[3xcex1,5xcex1-dihydroxy-2-(3xcex1-hydroxy-5-(5-(2,3-dibromo)thienyl)-1E -pentenyl)cyclopentyl]-5Z-heptenamide; 7-[3xcex1,5xcex1-dihydroxy-2-(3xcex1-methoxy-5-(2-furanyl)-1E-pentenyl)cyclopentyl]-5Z-heptenoic acid; and 7-[3xcex1,5xcex1-dihydroxy-2-(3xcex1-methoxy-5-(3-(2-methyl)thienyl-1E-pentenyl)cyclopentyl]-5Z-heptenoic acid. The entire disclosure of WO 97/31895 relative to the foregoing compounds is incorporated herein by this reference. Although the free acids of the above mentioned compounds, and other EP4 agonists/partial agonists, would be the active agents eliciting the beneficial effects at EP4 receptor, the use of esters and other derivatives of the compounds are also encompassed in the present invention.